1. Field of the Invention
This invention relates generally to determining angular position and velocity of a shaft and, more particularly, to using digital means for determining angular position and velocity of a shaft.
2. Description of Related Art
This invention relates to determining angular position and velocity of a shaft by using the electrical outputs of a resolver. A resolver is a type of sensor for determining the rotational position of an axis or shaft, such as a motor shaft. Generally, resolvers have one rotor winding and two stator windings. The two stator windings are typically mechanically arranged so that they are orthogonal to each other (i.e., 90 degrees apart). This physical spacing creates an electrical relationship such that any signals induced in the stator windings from the rotor windings are 90 degrees apart. Since the windings are 90 degrees apart, the relative amplitude of the signals in the stator windings are sine and cosine functions corresponding to the shaft angle being measured. By measuring the amplitudes and taking the arctangent function, it is possible to derive the shaft angle.
These output signals from the two stator windings are generally analog signals, which may require a significant amount of analog electronics to evaluate the signal amplitudes and derive the shaft position. As a result, many proposals use analog-to-digital converters to convert the analog signals to digital signals, which may then be manipulated digitally to determine the respective amplitudes and calculate the trigonometric functions to determine the shaft position. However, even these solutions may require complex analog-to-digital converters, and complex arithmetic engines for determining the signal amplitudes.
There is a need for a method and apparatus that reduces the complexity and number of analog components used in determining angular position and velocity by using simple analog components coupled to flexible digital logic and digital signal processing.